Motor-driven compressor



Oct. 5, 1948. R.-T. CORNELIUS MOTOR muvm: COMPRESSOR 5 Sheets-Sheet 1Filed Oct. 1, 1943 1 Q S n 4 v .m m w .m o M A. T w d w r 4 m u .m R 0 6m .1 4 m: 3 B w B.

176 fig-1 R. 1'. CORNELIUS 2,450,468 v UOTOR DRIVEN COMPRESSOR ssheets-sheet 2 f/i'li 4H 177 Oct.'5, 1948.

Filed Oct. 1, 1943 Richard T. Cornelius \&F

ttpr neg:

Oct. 5, 1948. R. T. CORNELIUS MOTOR DRIVEN COMPRESSOR 5 Sheets-Sheet 3Filed Oct. 1, 1943 lqveqtor Richard T. Cornelius 7 Am omega Oct. 5,1948. R. 'r. CORNELIUS MOTOR DRIVEN COMPRESSOR 5 Sheets-Sheet 4 FiledOct. 1, 1943 a. as 5 $13 5 I Inventor Richard T. Cornelius gt or megsOct. 5,1948. R. T. CORNELIUS 2,450,468

MOTOR DRIVEN COMPRESSCR Filed Oct. 1, 1943 5 Sheets-Sheetfi InveqbpryRichard Qbrneliu v Amer-neg:

Patented Oct. 5, 1948 UNITED STATES PATENT OFFICE MOTOR-DRIVENCOMPRESSOR Richard T. Cornelius, Minneapolis, Minn.

Application October 1, 1943, Serial No. 504,556

11 Claims. 1

My invention relates to motor driven compressors and has for an objectto produce an extremely practical and efilcient compressor forcompressing air and other fluids to relatively high pressures.

Another object of the invention resides in providing a relatively lightand compact construction.

An object of the invention resides in providing a multiple stepcompressor in which the disadvantages due to freezing of condensationare overcome.

A still further object of the invention resides in the specificarrangement of the compressor, the reservoir and connecting conduits bymeans of which flow of air to the reservoir is maintained at alloperating temperatures.

A still further object of the invention resides in providing a multiplestep compressor in which the air or other fluid compressed issuccessively cleliver'ed from one stage to the other and to a reservoirthrough conduitsarranged so as to cool the fluid and to causecondensation in the fluid to drain toward the following compressor unitor reservoir.

Another object of my invention resides in providing a construction bymeans of which the operating parts may all be readily lubricated,whereby the compressor can be'run at a high rate of speed.

A still further object of the invention resides in providing mechanismfor controlling the final pressure of the compressor.

Further objects of the invention reside in the novel combination andarrangement. of parts and in the details of construction hereinafterillustrated and/or described.

In the drawings:

Fig. 1 is a plan view of a motor driven compressor illustrating anembodiment of my invention.

Fig. 2 is a vertical sectional view taken on line 2-2 of Fig. 1.

Fig. 3 is a fragmentary vertical sectional view taken on line 3-3 ofFig. 1.

Fig. 4 is a fragmentary vertical sectional view taken on line 44 of Fig.1.

Fig. 5 is a detailed sectional view taken on line 55 of Fig. 2.

Fig. 6 is an elevational view showing the compressor and reservoir inposition.

My invention comprises an electric motor I which operates threecompressor units I I, I2 and I3. The compressor unit I I is a lowpressure unit, the compressor I2 is an intermediate pressure unit, whilethe compressor I3 is a high pressure unit. These various parts arecarried by a case which is indicated in its entirety by the referencenumeral I4. The high pressure unit I3 discharges into a reservoir 20.These parts will now :be described in detaill The motor I 0 consists ofa housing I which supports a stator core IS. The core I6 is constructedin the usual manner and carries coils I! which form the field of themotor. Within the core I6 is rotatably mounted an armature l8 which hasthe usual winding I9 thereon connected to the bars of a commutator 2|.The armature I8 is mounted onan armature shaft 22 which is journaled atits upper end in a bearing 23 mounted in an end bell 24 which is securedto the upper end of the housing I5. The end bell 24 carries brushholders 25 in which brushes 26 are slidably mounted for engagement withthe commutator 2|. The other'end of the armature shaft 22 is rotatablymounted in a bearing 21 carried by a seal 29 encircling the shaft 22 andmounted in partment 35.

the partition 28 prevents the passage of air or lubricant from the crankcase 36 to the motor com- For the purpose of cooling the motor Ill, airholes 2I3 are formed in the motor housing I5 below the armature I8 andother air holes 2M in the end bell 24 above said armature. The lower endof the armature shaft 22 is threaded as indicated at 3i to receive acrank 32 which is rigidly screwed thereon. This crank is provided with acrank pin 30 to which is attached a ball bearing 33 which serves tooperate the various compressor units. The crank 32 is provided with acounterweight 34 which counterbalances the weight of the crank 32, thebearing 33 and the other parts connected therewith.

The low pressure compressor unit II is best shown in Fig. 2 and consistsof a cylinder 31. Cylinder 31 is formed with a bore 38 which extendsthrough the same and is closed at its outer end by means of a cylinderhead 39; The inner end of the cylinder 31 which is indicated by thereference numeral 4|. extends through an opening 42 in the case I4.Screws 63 pass through a clamp 44 mounted on the end of the cylinderhead 39 and are threaded into the housing I4. These screws hold theparts in proper assembled relationship. Within the bore 38 of cylinder31 is slidably mounted a piston 45 which is operated by a connecting rod46. Connecting rod 46 is pivotally connected at one end to the piston 45by means of a wrist pin 41 and is formed at its other end with a boss 48in which the bearing 33 is mounted. As the armature shaft 22 of motor Irotates, the connecting rod 45 and the piston 45 are reciprocated.

The cylinder head 39 is formed hollow to pro vide a compartment withinthe same opening at its outer end and closed at its inner end by a wall52 forming part of said cylinder head. The wall '52 is provided with avalve seat 53 which encircles the same near the outer periphery thereof.Extending throughthis valve seat are a number of openings '54 whichbring the bore 38 of cylinder 31 into communication with the chamber 5I.A disk valve 55 seated on the valve seat 53 serves to close the valveand obstruct passage through the openings 54. The disk valve 55 isnormally held seated against the valve seat 53 by means of compressioncoil spring 58, which at one end engages said valve disk and at itsother end engages a flange 51 formed on a tubular stop 58. The flange 5iis clamped in posi-- tion in a rabbet 59 formed in the end of thecylinder head 39. Said flange is held in position by means of a cap 6|which bears against said flange and is also received within the rabbet59. The cap 6| is urged into position by means of the clamp 44 and thescrews 43 previously referred to. The stop 58 serves to hold the spring55 in proper position'and the end thereof terminates short of the valvedisk 55 and limits the movement of said disk away from the valve seat53. In this manner, the distance that the valve disk raises is limitedso that a short travel for the valve disk is provided and a minimum lossof the fluid compressed is produced when the piston reaches the end ofits stroke.

Air is introduced into the cylinder 31 through a crescent-shaped port 62which is formed in the cylinder 31 at the proper locality. The airentering the bore 38 of cylinder 3'I'passes through an air filter 63which is constructed with a case 64 having a chamber 65 within the sameopen to the exterior. A pad of filter material 56 extends across theopening in chamber 65 and is held in position by means of tworeticulated plates 61 and 88. The case 53 has a pipe fitting 69 formedon it which is screwed into a threaded hole II formed in the cylinder 31which communicates with the port 62.

The fluid compressed is conducted from the chamber 5| through a pipefitting 12 which is threaded into the cylinder head 39 and communicateswith said chamber. This pipe fitting has a tube 13 connected to itwhich, in turn, delivers the compressed fluid to the compressor unit I2as will be presently described.

For a purpose to be presently described, the low pressure cylinder 31 isof ample proportions to-furnish the fluid utilized by the other twocylinders. Under certain conditions, its capacity exceeds that requiredand for this purpose,

a pressure relief valve indicated in its entirety by the referencenumeral 14 is employed. This relief valve is shown in Fig. 2 and isconstructed as follows: In the center of the cap BI is formed adischarge opening 15 which is encircled by a valve seat 16. This openingcommunicates with a chamber 8| formed in the clamp 44 which, in turn,communicates with the exterior through openings 19 in said clamp. A diskvalve 11 seats against this seat and is urged into engagement therewithby means of a compression coil spring 80 which at one end engages saiddisk valve and at its other end engages the clamp 44. When the pressurewithin the chamber 5| becomes too great, the valve 14 is opened and theexcess fluid escapes through the opening I5 in the cap BI and throughthe openings I9 in the clamp 44 to the exterior.

The intermediate pressure compressor unit I2 is best shown in Fig. 4 andcomprises a cylinder 92 having a bore 83 therein of smaller dimensionsthan the bore 38 of cylinder 31. The end III 01 the cylinder 82 isreceived in an opening II2 formed in the case I4. Said cylinder has aflange II3 extending outwardly therefrom, which is secured to the saidcase by means of screws Hi4 passing through said flange and screwed intothe case. In the bore 83 is slidably mounted a piston 84, which isconnected by means of a wrist pin 85 to a connecting rod 85. Connectingrod 86 is pivotally connected to the boss 48 of connecting rod 96 bymeans of another wrist pin 91. As the crank 32 operates, piston 80 isreciprocated within the bore 83 of the cylinder 82. At the outermost endof the cylinder 82 is formed a tubular extension 88 which has a boretherein providing a chamber 89 of dimensions somewhat greater than thediameter of the cylinder bore 83. Disposed within said chamber andencircling bore 83 is a valve seat 9i. A valve disk 92 seats on saidseat and controls the flow of fluid from the cylinder 83. A compressioncoil spring 93 acts between said valve disk and a flange formed on atubular stop 95 similar to the stop 58 of the compressor unit II. Thisstop has an annular portion 96 which flts within the bore of thetubular-extension 80 and which is held in place therein by means of aring 91 seated in a groove 98 in the wall of said tubular extension. Anumber of openings 99 in the flange 94 bring the chamber 89 intocommunication with a passageway m formed in a tube fitting m. The tubefitting I02 is attached to the end of the tubular extension 88 by meansof a clamp nut I03 which is screwed upon threads I04 formed upon theexterior of the tubular extension 88. The fitting I02 has a tube I05brazed or otherwise secured to it and conducts the fluid entering thepassageway IN to the high pressure compressor unit I3.

The fluid to'be compressed enters the cylinder bore 83 through acrescent shaped port I01' which is formed in the wall of the cylinder82. This port communicates with a passageway I03, which, in turn,communicates with a tube fltting I09 screwed into the cylinder 82. Thetube I3 previously referred to, is connected to this fltting.

The high pressure compressor unit I3 is shown in detail in Fig. 4 and issimilar to the unit II. This unit comprises a cylinder II5 having a boreII6 therein extending completely through the same. Said cylinder isconstructed with an extension II! which is received in a hole I I8 inthe case I4 opposite the hole 2. The cylinder III has a. flange II9extending outwardly therefrom which is secured to said case by means ofscrews I2I. In the cylinder H5 is slidably mounted a piston I22 which isformed with an enlarged end I23. A connecting rod I24 is connected tothe end I23 of piston I22 by means of a wrist pin I25. 4

bore H6 is a valve seat I29 similar to the valve seat 9| which is closedby means of a disk valve I'3I. Valve I9I is normally held seated bymeans of a compression coil spring I32 whi'dh at one end bears againstsaidvalve disk and at its other end against a stop I33. The stop I33 issimilar to the stop 95 and is attached to the tubular extension I21 inthe same manner. Secured to the outer end of said tubular extension is atube fitting I34 which has a tube connector I35 formed thereon. Thisfitting is held in place by means of a clamp nut I36 similar to theclamp nut I63. The fiuid to be compressed is delivered into the cylinderII6 through a port I31 formed in the cylinder II5. A tube fitting I38 isscrewed into the cylinder I I5 and communicates with this port. Thistube fitting has connected to it the tube I66 leading from theintermediate pressure compressor unit I2.

The various compressor units are lubricated by means of a lubricatingoil pump I4I illustrated in detail in Fig. 2. Beneath the case I5 ismounted an oil sump I42. This oil sump is in the form of a tubularreceptacle with a bottom I49 and 2. cylindrical wall I44. The wall I44is constructed at its upper end with an offset I45 which extends about alip I46 formed on the lower end of the case I5. A gasket I41 carried bythis lip engages the inner surface 'of the offset I45 and forms afluid-tight connection therebetween. The sump I42 is detachably heldsecured to the case I4 by spring clips I48 best shown in Fig. 3, whichsnap under the ofiset I45. These clips have finger pieces I49 by meansof which the same can be disengaged from the oiiset. Screws I5I holdsaid clips attached to the case I4.

Within the sump I42 is mounted a cylindrical housing I52. This housinghas three ears I53 formed thereon, which are secured by means of screwsI 55 to bosses I54 extending inwardly from the lip I46 of case I4. Thehousing I52 has an upper end wall I56 and a partition I51 spaced fromthe extreme lower end thereof. In the end wall I56 and in the partitionI51 are provided bearings I58 and I59 which rotatably support a verticalextending shaft NH. The shaft I6I extends upwardly into the crank casecompartment 36 and has attached to its protruding end a driving memberI62. The driving member I62 has a flange I63 through which an extensionI64 of the crank pin 36 of the crank 32 extends. The shaft I6I iscoaxial with the armature shaft 22 so that as the armature I8 rotates,shaft I6I is driven in unison with it. Within the cylindrical housingI52 and by means of the partition I51 is formed at the lower end of saidhousing a downwardly opening compartment I65. Shaft I5I extends intothis compartment. Attached to the lowermost end of the shaft I6I anddisposed within the compartment I65 is the rotor I66 of a centrifugalpump, indicated in its entirety by the reference numeral I61. Adischarge passageway I63 is formed in the housing I52 and communicateswith the compartment I65. This passageway extends into the crank casecompartment 36 and is adapted to discharge the oil from the sump I44into the crank case, where the same lubricates the various pistons,connecting rods, crank and wrist pin bearings. The surplus oil drainsback into the sump I42 between the ears I53. In this manner, all of theoperating parts of the device except the motor bearings, are lubricated.

- I2 and I3, respectively, are also formed with radiating fins I12. Atthe top of the device and attached to the protruding end I13 of thearmature shaft 22 is a fan I14. This fan is of a' I greater diameterthan the diameter of the crank der side of the diaphragm case I4 and themotor housing I5 and serves to force air downwardly along the same. Partof the air so conducted passes through the fins of the variouscompressor units II, I2 and I3, and cools the same. Another portion ofthe air is forced by said fan through the holes 2I4 in end bell '24 andis directed into the motor compartment 35. The air leaves thiscompartment through the holes 2I3 formed in the case I4. A guard I15,secured to the end bell 24, protects the fan I14.

In order to control the operation of the device, an automatic switchmechanism is employed which is mounted in a switch box I11 which isattached to the motor housing I5. This switch box has side walls I18 andI19, upper and lower walls I86 and I82 and a rear wall I63. The wall I83has ears I84 projecting outwardly therefrom through which cap screws I85extend. These cap screws are threaded into the housing I5 and serve toattach the switch box to the device. Mounted Within the box I11 is anelectric switch I6I, which is connected in the circuit operating themotor I6. A plug I96, carried by the wall I19 or box I11 permits itconnecting the motor to a source of electric energy. .Inasmuch as theswitch I 8! forms no particular feature of the instant invention, theconstruction thereon has not been shown in detail. This switch, however,has a button I66 projecting outwardly therefrom, which is normally urgedoutwardly through suitable spring means and which, upon depression, isadapted to open the switch. When pressure is relieved on this button,the switch automatically closes.

The switch IIII is operated by means of the following construction:Formed on the wall I18 of box I11 is a boss I81, which is threaded toreceive a bushing I88. A tube connector I89 is screwed into this bushingand has connected to it a tube I9I. Tube MI is connected to the fittingI34 of the compressor unit I3 and brings the chamber I92 within thebushing I88 into communication with the high pressure side of thecompressor unit I3. Extending across the end of the bushing is adiaphragm I93 which is clamped by means of said bushing against a seatI94. A follower I95 bears against the un- I93. Mounted for swingingmovement within the box I11 is a lever I96, which is pivoted on afulcrum I'91 which is attached to a boss 266 on the rear The entirecompressor is cooled in the following wall I63 ofbox I11. Alink I96extends between the lever I66 and the follower I and I93 to The extremeend of lever I96 transmits motion of the diaphragm said lever I95. isengaged by a spindle I99 which has a conical head 2! at the extreme endthereof which'is seated in a suitable socket 262 in said lever. SpindleI99 is slidably mounted in a guide 262 screwed into a boss 264 issuinginwardly into the box I11 from thewall I19 thereof. A compression coilspring 265 encircles the spindle I99 and urges the same into engagementwith the lever I96. Movement of the lever I96 in a counter-clockwisedirection is terminated by means of an adjustable stop 266 which iscarried by the wall I18 of box I11. The lever I96 carries an adjustablestud 261 which engages the button I36. As the diaphragm I 93 moves,lever I36 is oscillated and operation of the switch I8I occurs. When thepressure produced by the high pressure unit I3 reaches the desiredamount which can be adjusted by means of thestud 201, switch I8I isopened and compressor stops.

For the purpose of supporting the compressor, the box II'l isconstructed with ears 2 which project outwardly therefrom. These earshave holes 212 therein through which suitable fasteners may extend toattach the compressor to a vertical support. The compressor ispreferably mounted above fioor level, so that the oil sump M2 may beeasily removed therefrom for the purpose of filling and inspection.

In conjunction with my motor-driven compressor, I employ a reservoirsuch as designated at 215 in Fig. 6 and into which the compressed air orgas is directed. This reservoir is tubular in form, having a cylindricalwall 23I, a lower end 232 and an upper end 233. This reservoir isconstructed in two halves, 236 and 28'! welded or soldered together atthe center, as indicated at M8. The reservoir 2I5 is arranged in verti-'cal position and is mounted on the support to which the compressor isattached. For the purpose of illustration, a channel frame member 2 l 9has been shown for this purpose. This frame member may be a portion ofthe aeroplane or other structure in which the compressor is to be used.Bolts 22E extend through the ears 2II f the compressor switch box I'lland through the web 222 of the channel 2'I9. Spacers 223 between saidears and web hold the compressor in proper position.

The reservoir 2I5 has attached to it a mounting plate 223. This mountingplate has secured to it bands 225 which encircle the reservoir properand clamp the mounting plate in position. The plate 224 overlies the web222 of channel 2I9 and the bolts 22I pass through the same. In thismanner, the reservoir 2I6 is mounted in proximity to the compressor andis supported by the same support.

The tube connector I35 which is formed on i the tube fitting I34associated with the compressor unit I3 has connected to it a tube 226.This tube is connected to a tube fitting 221 which is screwed into aboss 228 secured to the reservoir 2I5. The inlet through the fittingtube 221 is disposed above the lower end 232 of the reservoir 2I5 andbelow the outlet in the tube fitting 234. It will thus be seen that thetube 226 inclines throughout its extent from the cylinder II! to thereservoir 2I5 and that the discharge is located above the lower end ofthe reservoir to form the space 229 above said inlet in which water maycollect. The tube 226 is covered with an insulating jacket 230.

Opposite the tube fitting 221 is a relief valve 234 which is threadedinto a bushing 235 secured to the wall 23I of said reservoir. At thebottom of the reservoir is a drain I which is secured to the wall 232.

Airis led from the reservoir to a. tube fitting 236 which is screwedinto a bushing 231 secured to the upper end 233 of said reservoir. Forthe purpose of preventing water and foreign material from entering thefitting 236, a filter 238 is employed which is supported by a perviousplate 239 secured to the wall 23I of the reservoir '2I5 below the upperend 233 thereof.

The operation of my invention is as follows: When the pressure producedby the high pressure unit I3 drops below a certain value, or when thedevice is being first started, pressure on the diaphragm I93 is releasedand the lever I96 urged against the stop 206 by means of the spring 205.This causes the switch I8I to close and energize the motor Ill. Theoperation of motor Ill causes simultaneous operation of the pistonswithin the various compressor units II, I2 and I3, and the compressionof the fiuids within the cylinder thereof. When the motor-drivencompressor comprising the instant invention is used at high altitudes,all of the air compressed in cylinder 37 is required to furnish thenecessary amount of air at the desired pressure to be successivelycompressed in the cylinders 32 and H5. When, however, the compressor isused at low altitudes, an excess of air would be drawn into the cylinder31. For the purpose of disposing of the excess air, the relief valve Mis employed. Spring Bil operating this valve is so designed as torelieve the pressure in cylinder 31 when the amount of air pumped by thecompressorunit H reaches the desired volume. It will be noted that thetube fitting I2 connected to the discharge end of the compressor unit Ilextends upwardly and that the tube I3 which is connected to it slopesdownwardly from this fitting to the inlet fitting N9 of cylinder 82,which inlet fitting is disposed at the lowermost portion of the cylinder32. By means of this construction, the condensation occurring in tube 13fiows downwardly from the unit II to the unit I2. To produce the samecondition in the tube I06 which is connected to the high pressure sideof the compressor unit i2, said tube extends upwardly from the fittingI02 and is then caused to travel downwardly toward its point ofconnection with thehigh pressure cylinder II5. Since the upstandingportion of tube I06 is short, condensation does not occur until the airreaches the inclined portion of the tube from which it drains into thecylinder H5 of unit 53. In this manner,

- condensation is caused to travel through the compressor from onecylinder to the other. When the air leaves the compressor I3, the sameflows through the tube 226 and into the lower end of the reservoir 2I5.Due to the insulating jacket 230, freezing of the water isprevented'during its passage through tube 226, Any water which may havebeen condensed from the liquid, flows into the bottom of said reservoirand is confined within the space 229. The air travels upwardly andpasses through filter 238 prior to its discharge from the reservoir,through the tube fitting 233. By arranging the conduits between thecompressor units and the reservoir as disclosed, pocketing of thecondensation is eliminated and the condensation discharged through thecompressor with the compressed air and into the reservoir, whereseparation occurs. When the pressure in the high pressure compress-orunit I3 reaches the desired amount, switch I8I is automatically closedas previously described. Whereupon the compressor ceases to function.

My invention is highly advantageous in that an extremely simple andpractical device is produced which will positively and effectivelyfunction to produce the desired results. With my invention, air can becompressed at difierent altitudes without adjustment of the apparatus.My i improved motor-driven compressor can beconstructed relatively lightin weight, so that the same may be installed, on the aeroplanes orwherever a light weight construction is desired. By means of thelubricating system employed with my invention, all of the parts arethoroughly lubricated, so that the compressor can be driven at a higherrate of speed. With the automatic switch m "chanlsm, the pressure ismaintained any desirable value. Adjustment of the pressure can bereadily made by adjusting the guide forming the spring seat for thepressure regulating device. Cooling of the compressor is procured by themotor operating the compressor :units. The sump for lubricating oilisreadily removed and inspectionof the interior of the compressor isreadily had upon removal of the same.

Changes in the specific form of myinvention as hereindisclosed may bemade within the scope of what is claimed without departing from thespirit of my invention. 1

Having described my invention, what I claim as new and desire to protectby Letters Patent is.

1. A compressor comprising a case, a motor mounted on the upper portionof said case and of diametral dimensions substantially the same as thoseof the case said motor including an armature shaft, a plurality ofcompressor units pro- Electing outwardly from said caseand extendingbeyond the confines of said motor and case, means for operating saidcompressor units from the armature shaft of said motor, said case andmotor having ventilating openings for conducting air through the motor,the armature shaftof said motor extending upwardly beyond the-same, and

a fan mounted on said armature shaft and proof said compressor unitsfrom said crank, a conduit having a reach extending upwardly from the.

discharge of a lower pressure compressor unit and anotherreach incliningdownwardly toward the intake of a higher pressure compressor unit,

the intake ,of said higher pressure compressor unit being disposed atthe uppermost portion thereof to cause condensation collected in saidlast-named reach to how by gravity into the higher pressure compressorunit.

3. In combination, a compressor having a high pressure cylinder, apiston in said cylinder, means for operating said piston, an inlet andan outlet for said cylinder, a reservoir, a conduit extending betweenthe outlet of said cylinder and reservoir and serving to discharge intothe reservoir,'said conduit inclining downwardly throughout its extent,the inlet from said conduit beingabove the bottom of said reservoir, anoutlet at the uppermost portion of the reservoir, and adrain at thelowermost portion of said reservoir.

4. In combination, a compressor having a high pressure cylinder, apiston in said cylinder, means for operating said piston, an inlet andan outlet for said cylinder, a, reservoir, a conduit extending betweenthe outlet of said cylinder and reservoir and serving to discharge intothe reservoir, said conduit inclining downwardly throughout its extent,an insulating jacket surrounding said conduit, the, inlet from saidconduit being disposed intermediate the upper and lower ends of thereservoir, an outlet at the uppermost portion of the reservoir and adrain in the' reservoir at a locality below said inlet.

5. A compressor comprising acase, a motor mounted on the upper end ofthe case and having an armature shaft extending into said case, a crankattached to said armature shaft and disposed within said case, saidcrank including a crank pin, a plurality of compressor units carried bysaid case and disposed radially with reference *to the moving partswithin said case.

6. In. combination, a multiple stage compressor comprising a plurality'of cylinders arranged horizontal ly and at substantially the sameplane, pistons in'said cylinders, means for operating said pistons,inlets and outlets for said cylinders, a conduit extending between theoutlet of a cylinder of lower pressure to the inlet of a. cylinder ofhigher pressure, said conduit at the locality of the first namedcylinder having a substantially upwardly extending vertical reach, and areach run ning between said vertical reach and the other cylinder andinclined substantially throughout its extent toward the second namedcylinder.

'7. In combination, a compressor having a hlgh pressure cylinderarranged in a horizontal posi-- tion, a piston in said cylinder, meansfor operating said piston, an inlet for said cylinder, an outlet forsaid cylinder comprising a discharge chamber atthe end of the cylinder,a vertically extending reservoir disposed adjacent said cylinder, aconduit connected to the under side of said discharge chamber and tosaid reservoir and serving to discharge into the reservoir, said conduitinclining downwardly throughout its extent, the inlet from said conduitto said reservoir being disposed intermediate the upper and lower endsof the reservoir, an outlet at the'uppermost portion of the'reservoirand a drain in the reservoir at a locality below said inlet.

8. A compressor comprising a case, a motor mounted on the upper end ofthe case and having a vertically extending armature shaft disposedwithln the case, a crank attached to said armature shaft and disposedwithin said case, a plurality of compressor units carried by the caseand extending radially with reference thereto, means for operating allof said compressor units from said crank, an oil sump disposed belowsaid case, means for detachably securing said sump to the lower end ofthe case, a pump housing disposed within said sump, means for detachablysecuring said pump to the lower end of the case, said pump having arotor at the lowermost por- 7 tion thereof, a shaft for driving saidrotor, said shaft being substantially coaxial with said armature shaft,said pump shaft having an eccentric part disposed adjacent acorresponding part on the crank, a pin on one of said parts and a holein the other of said parts for the reception of said pin for restrainingrelative movement between 5 said shafts and forming a driving connectionbeprojecting outwardly from said case and extendassociated with said ingbeyond the confines of said motor and case, an oil sump disposed belowsaid case and being of substantially the same diametral dimensions assaid case, means for operating said compressor units from the armatureshaft of said motor, said case and motor having ventilating openings forconducting air through the motor, the armature shaft of said motorextending upwardly beyond the same, and a fan mounted on said armatureshaft and projecting radially outwardly beyond said motor and case, saidfan serving to force air past said compressor unit and sump and throughsaid motor.

10. A multiple stage compressor comprising a plurality of cylindersarranged in coplanar horizontal relation, pistons therein, means forsimultaneously operating said pistons at predetermined relative speeds,said cylinders being proportioned to procure different pressurestherein, a lower pressure cylinder having an inlet and a dischargeoutlet and the cylinder of the next higher pressure having an inlet anda discharge outlet, a conduit extending between saidcylinders and havinga vertical reach extending upwardly from the outlet of said lowerpressure cylinder and a downwardly inclining reach extending from theuppermost portion of the vertical reach to the inlet of said higherpressure cylinder to cause most of the condensation collected in saidconduit to flow by gravity into said higher pressure cylinden- 11. Amultiple stage compressor comprising a plurality of cylinders arrangedin coplanar horizontal relation, pistons therein, means forsimultaneouslyoperating said pistons at pre-determined relative speeds,said cylinders being proportioned to procure different pressurestherein, a lower pressure cylinder having an inlet and having adischarge outlet at the uppermost portion of the same and the cylinderof the next higher pressure having an outlet and having an inlet at theuppermost portion of the same, a conduit between said cylinders having avertical reach extending up- I REFERENCES CITED The following referencesare of record in th file of this patent:

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